To Loctie or not to Loctie, that is the dilemma

garibaldi · 03-01-2004, 10:09 AM

Allow me some humor here.

When I open a bottle of Red Loctite, the aroma of cherries fills the air. I dab a little bit behind my ears, rub some on my teeth and greet the day. I use it on sandwiches and in mixed drinks. Its great for diarreah, poison ivy and muscle cramps. It works better than viagra if you rub it on the nether regions, I have only gotten one complaint. Many virgins have been known to use a drop or two on the bra clasps and garter connections.

When I build an engine, I also use it liberally on the front and back of the main and rod bearings, on the valve stems and inside the guides, under the valve face where it meets the seat, I prime the oil pump with Red Loctite and drop a dash or two, or three in the gas tank before I fire her up. I just cant figure out why the engines dont turn over.

Ok, time to get get serious, the previous statements where to wake you up and lighten you up.

LOCTITE IS A BANDAID. ENGINEER AT THE SOURCE- THE ROD BOLT. If you think Loctite is going to save your ass if your bolts stretch beyond their limits, your dreaming!

For arguments sake, lets just concentrate on Porsche rod bolts. These bolts are engineered to operate, and operate well within a confined envelope. If they are taken outside that envelope you are in deep water. SOME rod bolts are are stretch to yield, and this puts you at the edge of the envelope and if taken beyond that limit you are merely cylcing the component beyond the edge of its safety margin. Loctite is not going to help you there.

A rod bolt is without a doubt a critical fastener in an engine, and it requires critical torque properties to operate properly. Using Loctite on the threads will not put you within the predictable torque range. Following the engineers instructions and using what the manufacturer recommends to achieve that torque is absolutlely critical. Usually this is a supplied lubricant, or substitued for with straight 30 weight oil (And not a 10-30 or other multi viscocity at that). Which is the old SAE standard. Locitite Is not a lubricant, it is a locking compound, and it does not posses the molecular properties while in its liquid state to be able to gain an accurate torque flow in a fastener, especially one that is going to rely on the specific torque in order for it to operate as designed.
So using it on the threads of your rod bolts is your choice. I sure would never do it.

If a fastener is free from defects, and installed and torqued properly and not operated beyond its intentions, there is no reason for it to ever come loose. The engineering in materials and thread pitch have come so far that it is no longer a black art.

In conclusion, when they fail you find the threaded section of the bolt if it thread into the rod- still in the rod, and the rest on the bolt in the case. And if it is a bolt and nut affair in the same case, then the failed rod bolt will be found in two- with the threaded end of the bolt with the nut still on it.

In closing, THE ONE THING TO USE IS YOUR HEAD

garibaldi · 07:03 PM

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garibaldi · 03-01-2004, 07:04 PM

Here is some rod bolts that failed, notice how the failure happened at the root of the base of the threaded section. These were torque to yield bolts. WITHOUT THE USE OF LOCTITE.

These did not loosen, they failed. When you take an engine way upstairs in the revs, the inertia will go crazy, and this is what you can end up with. The force of the mass goes up by the square of the RPM. A 280,000 psi bolt can get dwarfed in this range.

rcwaldo · 03-01-2004, 08:10 PM

Some great discussion from the other thread about loctite and rod bolts. I agree with the notion NOT to loctite rod bolts, especially since Loctite will alter the torque reading etc.

If one were super paranoid, and insisted on using loctite, there is a loctite that is called 'wicking' loctite. Its basically a super low viscosity loctite (green strength) used to 'wick' into tight areas such as press fit bearing races etc.

Just torque rod bolts as recommended, then apply a small amount of wicking loctite at the end of the nut/rod bolt.

Chris

garibaldi · 03-02-2004, 08:09 AM

The only proper way to torque a rod bolt in this case is to use the proper lubricant, which is usually a specified weight oil or a lubricant supplied by the bolt manufacturer. These lubes are petroleum based and will give you the proper friction characteristics to achieve proper torque. Loctite does not posses any of these characterictics, and is not advertised to do so. Sure it is a liquid and slippery, but then so is water, so why not use that on the threads? See the logic? You should never torque any fastener dry, and should always use a lubricant is a specific case such as this. Loctite does not cut it at all.

As far as the wicking type of Loctite, in order for a proper Loctite bond to occurr, the surfaces must be clean and free from any dirt or petroleum based product for it to set up. So if the rod bolt were torqued properly using the proper lubricant, then using the wicking type Loctite afterward would be useless because when it wicks into the threads- IF it wicked into the threads (The oil in the threads would create a barrier preventing the Loctite to wick), it would not be able to achieve adhesion due to the contamination from the lubricant already there.

Bottom line is that Loctite should not be used on rod bolts, and if it is used, then the fastener will not be torqued correctly, so you would have a better chance of having a failure of the unit if that was used instead of the proper thread lubricant in the first place.

Wayne 962 · Wayne 962's Garage

I disagree. The problem with stretching on the late-model rod bolts is well documented. Unfortunately, your pics of rod bolts failing in the above picture (I have one just like it in the Engine Rebuild Book) may be caused by a number of factors, unrelated to the actual rod bolt itself. It's possible that one rod bolt comes loose, which causes itself or the other one to snap. Simply stating that the rod bolt failure mode is the snapping is a premature conclusion. The rod bolt coming loose is apparently what happened in the photo that is on page 82, Figure 4-12.

For the Engine Rebuild Book, I put in many hours of research on this and other subjects. Some rebuilders I spoke to used Loctite, some didn't. In general on the early cars, it's a non-issue, as rod bolts almost never fail on these engines. On the later cars, I believe that adding the Loctite will give you an added margin of safety. If the bolt stretches and doesn't have Loctite on it, then the nut will immediately fall off. If there is Loctite on it, then it has a more likely chance of staying attached to the bolt, at least so that you can pull over to the side of the road and figure out what that noise coming from your engine is.

I believe that this added margin of safety offers no downside risk, with the potential to save your engine. It is important to note that in the book I recommend several things that the factory didn't originally. These recommendations are based on the collective knowledge of many engine rebuilders, and are often designed to overcome shortcomings in the factory designs that are known to fail.

-Wayne

Wayne 962 · Wayne 962's Garage

Quote:

Originally posted by garibaldi
If a fastener is free from defects, and installed and torqued properly and not operated beyond its intentions, there is no reason for it to ever come loose. The engineering in materials and thread pitch have come so far that it is no longer a black art.

Yes - all true, but you are forgetting something too. The fastener has to have an ample margin of saftey in the design as well. It would appear that Porsche under-designed this component on the 3.2/3.3/3.6 engines and thus has been plagued with numerous failures. This is why I do not recommend using factory rod bolts under any circumstances in these engines, when performing a rebuild. In addition, the Loctite adds an additional margin of safety, on a proven weak point in the engine.

It's also common for VW rebuilders to use Loctite on the rod bolts.

-Wayne

garibaldi · 03-02-2004, 12:35 PM

It is obvious that some of the collective knowlege that you obtained to use in your book is wrong.

garibaldi · 03-02-2004, 01:10 PM

Wayne, everywhere I look on this site, every post you seem to make, and every response I have read from you does little more than plug the book you wrote. I seems obvious that you are more interested in book sales than the TRUTH and bettering of the breed.

I think it would be in very poor taste for me to come out and damage my reputation by telling you where you are wrong and what I know.

garibaldi · 03:47 PM

No disrespect, but in response to your comment on someone hearing a clickety click noise in the motor, and the Loctite giving you some extra time to pull over and save the engine, the guy who had the remnants in the picture I posted uphere heard the noise....... and pulled over, but the I dont think that the Loctite would have helped.

blue72s · 03-02-2004, 04:12 PM

Watch the DVD - "Porsche, one for the road" made in 1973. You'll see how the factory worker installed con rods and rod bolts...

OIL OIL and more OIL

rcwaldo · 03-02-2004, 06:03 PM

Quote:

Originally posted by garibaldi

As far as the wicking type of Loctite, in order for a proper Loctite bond to occurr, the surfaces must be clean and free from any dirt or petroleum based product for it to set up. So if the rod bolt were torqued properly using the proper lubricant, then using the wicking type Loctite afterward would be useless because when it wicks into the threads- IF it wicked into the threads (The oil in the threads would create a barrier preventing the Loctite to wick), it would not be able to achieve adhesion due to the contamination from the lubricant already there.

I wouldnt call it useless, but yes, I completely agree, for a proper loctite bond, all surfaces must be degreased and with stainless and Ti materials, a loctite primer has to be used.

You would be amazed at the bonding ability of loctite, even with an oily surface involved. An example is we have a few coupler nuts inside a racecar gearbox where antiseize (Copaslip) had to be used to prevent galling and false torques upon assembly. After torqued to 250ft/lbs., we had a problem with this input shaft coupler nut coming loose on several occasions. The fix was to apply a small amount of wicking loctite after assembly, which luckily cured the problem. Removing these nuts were unbelievably tough. Eventually we learned that mixing standard red 272 loctite with Copaslip provided ultimate situation making this particular nut easier to work with.

Excuse me for straying off-topic in regards to rod bolt applications, I didnt mean it..... really

garibaldi · 03-02-2004, 06:28 PM

Is there any specific ratio that you mix the antiseize and loctitie at?

Wayne 962 · Wayne 962's Garage

Quote:

Originally posted by garibaldi
Wayne, everywhere I look on this site, every post you seem to make, and every response I have read from you does little more than plug the book you wrote. I seems obvious that you are more interested in book sales than the TRUTH and bettering of the breed.

First of all, the book speaks for itself. I do not like to repeat myself when I have already spent 1,500 hours researching and writing a book on the subject. If there is information that is in the book, then I point people to that information.

Quote:

Originally posted by garibaldi
I seems obvious that you are more interested in book sales than the TRUTH and bettering of the breed.

This is funny. Perhaps you should read some of the 100s of technical articles I've written, or look at some of the other 8000 posts on this BBS before you mouth off like that.

Quote:

Originally posted by garibaldi
I think it would be in very poor taste for me to come out and damage my reputation by telling you where you are wrong and what I know.

I think that you have already shown rather poor taste already in your replies to my posts on this thread.

In this world, there will always be pundits. The world is not black and white, there are shades of grey to everything, and in this case, there is no definitive right or wrong answer. The book has been based on plenty of good research and it stands on its own. I would guess that you haven't seen it. I don't need to defend it - it speaks for itself.

-Wayne

Wayne 962 · Wayne 962's Garage

The absolute proper way to tighten these bolts is not with a torque wrench, but with a stretch gauge, which actually measures the stretch length of the bolts. This is really what matters, not the actual torque reading on a rotated fastener.

Jerry Woods uses one of these stretch gauges to make the point in his engine rebuild class. If you really want to to wild - use one of these gauges and use the Loctite as well. Since the stretch of the bolt is not affected by the application of the Loctite, there should be no changes in the resulting final torque.

One of these days, I will have to dig out a stretch gauge, and measure the total stretch on one rod bolt while using oil as a lubricant, and also on another using just Loctite.

-Wayne

Britwrench · 07:27 PM

I have seen plenty of different makes of engines and can't recollect any sort of locking chemical being used. This includes watching the factory technicians assemble 911 engines.

Regarding the 3.2 rod bolts, the failures usually occur due to abuse (over-revving) causing rod bolt strech, not bolt loosening.
Once the rod bolt tension is lost and therefore also bearing clearance and crush, no chemical in the world is going to stop rod bearing failure, loss of oil pressure, bearing spin and rod bolt breakage. On a high-rev 3.2 you should always use better quality rods.

As with the picture on the post, we lost a 427 cu. in. BBC last year due to oil pressure failure. The bearing then span and subsequentially the rod bolts broke.

garibaldi · 03-02-2004, 08:15 PM

Wayne you are turning this into a gun fight. I was merely trying to share some information.

Fisrt I will adress the other two guys who posted right after you

Noah; I feel like I am invading Wayne's house. This is his engine building forum after all, I am just a guest. I was raised better than that. I unfortunately cannot point you to a book I wrote, or a website to take this elsewhere. The information that I have is by no means secret and I would be more than happy to share it with you. Wayne should give permission though, since it is going to go against some of the stuff he writes about in his book. This is not slander, its simple ethics, and EXPERIENCE, which I am now questioning from the opposing side. This is a discussion of differences in philosophy.

I will do you one better, and I invite anyone interested to see for yourself. I ENCOURAGE YOU TO DO THIS! Get off your tail and find out for yourself, not just take someones word for it:
Wayne, dig out your stretch gauge and find out the differences with using the various compounds, but dont just use loctite and oil, try STP, try it dry, try it with anti- seize, gather some data. Measure the stretch and torque angle. FInd out how much longer the bolt will stretch in each instance to reach the same torque. Find out if the bolt is loaded with the same tension when it is at the particular torque.

For everyone else, take the time and look up on the web for the ARP website, I am sure they have an email or toll free number, call them up and speak to someone in engineering and ask them what they would recommend using during assembly of their rod bolts. Be sure to throw in the idea that you were going to consider using Loctite, and see what they think. That way you can get another opinion.
I am sitting here right now writing this and staring at the back of a box of ARP fasteners that not only has a chart that clearly shows approximate torques for their various fasteners, with one column for ARP assembly lube, and the other column with a different torque if you are using 30 weight oil- but right next to that it gives more information on how important the proper lubricant is when assembling a fastener. FInd out for yourself.

Britwrench, you are absolutely right. You would be more likely to have a failure if you used the loctite, since in doing so, the rod bolts are not going to be torqued properly to begin with, so its anyone guess if they would loosen up rather than if they were installed properly from the onstart. The onyl time I have heard of a rod bolt loosening up and unscrewing inside an engine on its own is because someone did not properly tighten it. And in these instances the pecker tracks are on the parting faces of the cap, and on the bernelling or transfer of metal on the back of the bearings.

Wayne, I apologize, I was not trying to repsond in bad taste. I am sorry I have some across that way. I do not think that I am acting as a pundit, I am not tormenting you, or stealing your wind. I am just sharing information.

camgrinder · 03-02-2004, 09:35 PM

That connecting rod in the picture is very black. If the rod bolt did not stretch and/or the housing bore did not go out of round and lose the bearing, then the rod big end should be normal color.
Were those ARP bolts? I can't believe an ARP 280,000 psi bolt could just break like that on thier own.

Randy Webb · 03-02-2004, 09:50 PM

Exactly. Even if not ARP, the socket design is that of a high strength aerospace bolt, AN or newer spec. UNlikely it would fail without something else going very wrong.

The statement re secret knowledge also suggests a lack thereof. If you have something held in confidence then don't mention it at all. If not, then let's hear it.

Wayne 962 · Wayne 962's Garage

Quote:

Originally posted by garibaldi
Wayne you are turning this into a gun fight. I was merely trying to share some information.

Wayne, I apologize, I was not trying to repsond in bad taste. I am sorry I have some across that way. I do not think that I am acting as a pundit, I am not tormenting you, or stealing your wind. I am just sharing information.

Not a problem. I am more than open to counter thoughts and counter-opinions on any topic. My word is not the absolute gospel, and I would hope that it isn't taken that way. In life, there are many "grey areas" where there are no definitive answers.

No man is an island, and it would have been foolish for me to write the book based soley on one person's opinions (mine). That is why I did research the finer elements of the book so much. The ironic thing is that for the many people I spoke with and conferred with about information for this book (Steve W., Bruce Anderson, Jerry Woods, Tom Woodford, Walt Watson) - I found many, many areas where all of these experts disagreed with each other on at least one topic. This was a very difficult situation for me, as I had to weigh all of this conflciting information together, filter it using my background in engineering (BS & MS from MIT) and then come up with a finished product. I personally think that I did a good job, and people (both novices and experts alike) seem to like and appreciate the finished product.

No hard feelings here - I actually welcome open forums (this is one). Just keep it on a friendly level.

-Wayne